package tcp;

import java.io.*;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.Scanner;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class TcpEchoServer {
    private ServerSocket serverSocket = null;

    public TcpEchoServer(int port) throws IOException {
        serverSocket = new ServerSocket(port);
    }

    public void start() throws IOException {
        System.out.println("服务器启动!");
        // 创建线程池
        ExecutorService pool = Executors.newCachedThreadPool();
        while(true) {
            // 通过accept方法"接听电话",然后才能进行通信
            Socket clientSocket = serverSocket.accept();
            pool.submit(new Runnable() {
                @Override
                public void run() {
                    processConnection(clientSocket);
                }
            });
        }
    }

    //通过这个方法来处理一次连接, 连接建立过程中涉及到多次请求的响应交互
    private void processConnection(Socket clientSocket) {
        System.out.printf("[%s:%d] 客户端上线!\n",clientSocket.getInetAddress(),clientSocket.getPort());
        //循环的读取客户端的请求并返回响应
        try(InputStream inputStream = clientSocket.getInputStream();
            OutputStream outputStream = clientSocket.getOutputStream()) {
            Scanner scanner = new Scanner(inputStream);
            while(true) {
                if(!scanner.hasNext()) {
                    //读取完毕,客户端断开连接,就会产生读取完毕
                    System.out.printf("[%s:%d] 客户端下线!\n",clientSocket.getInetAddress(),clientSocket.getPort());
                    break;
                }
                //1.读取请求并解析 next要读到空白符才会结束
                String request = scanner.next();
                //2.根据请求计算响应
                String response =  process(request);
                //3.把响应返回给客户端
                //通过这种方法可以写回, 但是这种方法不方便给返回的响应中添加\n
                    //outputStream.write(response.getBytes(),0,response.getBytes().length);
                //也可以给 outputStream 套上一层,完成更方便的写入
                PrintWriter printWriter = new PrintWriter(outputStream);
                printWriter.println(response);
                printWriter.flush();

                System.out.printf("[%s:%d] req: %s, resp: %s \n",clientSocket.getInetAddress(),clientSocket.getPort(),
                        request,response);
            }
        } catch (IOException e) {
            throw new RuntimeException(e);
        } finally {
            try {
                clientSocket.close();
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }
    }

    public String process(String request) {
        return request;
    }

    public static void main(String[] args) throws IOException {
        TcpEchoServer server = new TcpEchoServer(9090);
        server.start();
    }
}
